Sewing machine for automatic contour stitching

ABSTRACT

This invention relates to apparatus associated with the stitching mechanism of a sewing machine for automatically feeding the fabric or work to be sewn through the stitching zone in a manner to sew a line of stitching along a predetermined contour which is not a straight line.

United States Patent Robert L. Kosrow Hoffman Estates, 111.

Aug. 14, 1969 Nov. 9, 1971 Union Special Machine Company Chicago, 11].

Inventor Appl. No. Filed Patented Assignee SEWING MACHINE FOR AUTOMATIC CONTOUR STITCHING 18 Claims, 20 Drawing Figs.

US. Cl. 1l2/12l.12

Int. Cl D05b 21/00 Fieldofsearch ..1l2/12l.12,

[5 6] Reference sT Zited UNITED STATES PATENTS 2,684,041 7/1954 Tice 112/121.l2 3,001,489 9/1961 Bond et al. l12/l2l.l2 3,034,458 5/1962 Bennison..... l12/121.l2 3,227,115 1/1966 Bono 1l2/l21.12 3,349,731 10/1967 Bono 112/121.l2 3,448,705 6/1969 Scherr et a1 112/102 X Primary Examiner-H. Hampton Hunter Attorney-John A. l-lowson ABSTRACT: This invention relates to apparatus associated with the stitching mechanism of a sewing machine for automatically feeding the fabric or work to be sewn through the stitching zone in a manner to sew a line of stitching along a predetermined contour which is not a straight line.

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TO ALL HOT T TERMINALS TO ALL ekouma TERMINALS n a 84 FvA 0 HO 5 a C3 H TC T U LL EC TIMER I75" CYLINDER HOFFMAN CIRCUIT STANDARD I S IDE SECTION CYLINDER SEWING MACHINE FOR AUTOMATIC CONTOUR STITCIIING The invention is concerned with automatic sewing apparatus wherein the various pieces of fabric to be stitched together are supported upon a low-friction surface against which they are lightly clamped down by a holddown member which is part of a suitable conveyor means adapted to frictionally engage the work and slide the latter past the stitching station. The conveyor means are arranged for a combined movement in two coordinate directions along a path controlled by a pattern member. The direction of movement of said conveyor means is determined by a cam follower member connected with said conveyor means. In operation this cam follower member is guided in a cam track slot, constituting the pattern in said pattern member. Thereby said holddown member engages the work, i.e., the upper layer of the work with a friction grip sufficiently strong to apply a frictional hold on the underlying layer or layers of the work material and move these layers along on a smooth work-supporting surface. The friction force applied to the upper surface of the work must be strong enough to exceed the friction generated between the bottom surface of the lowest underlying material layer of the work and the work-supporting surface which to this end is preferably formed of low-friction material such as, for example, high-polished metal, Teflon or Mylar. The work to be sewn is caused to slide upon the work-supporting surfaces by the differential in friction existing on one hand between the holddown member and the underlying layers of material, and, on the other hand, between the bottom surface of the lowest underlying layer of material and the work-supporting surface.

It is well known in the art that when workpieces of relatively limp nature are to be joined together by sewing along a line which is not a straight line, there is placed considerable reliance on the skill of an operator. The necessity of the operator to stay with the work throughout the operation and guide the workpieces through the stitch-forming zone along an irregular or curved line requires not only a high amount of concentration of the operator, which often times leads to early and excessive fatigue of the latter, but also results in the consumption of a considerable percentage of the total cycle time of the operation.

It is therefore the primary object of the present invention to provide an automatic sewing apparatus which is capable of producing an irregular or curved line of stitching automatically and without requiring guidance by the operator.

It is another object of the present invention to provide a sewing apparatus of the general type outlined above, having work-guiding means adapted to automatically feed the work under the needle at a relatively high rate of speed with precision and accuracy and with a minimum amount of personal attention so that a single worker can supervise several such automatic sewing machines.

It is a further object of this invention to provide a pattern member having a cam track slot cooperating with a cam follower means which is movable in said slot from one terminal position to another terminal position.

It is still another object of this invention to provide apparatus as above wherein a material holddown member is connected with means associated with said cam follower means, and said associated means are adapted to transmit the movement of the cam follower means in more than one coordinate direction, to said work holddown member.

It is also an object of the present invention to provide a sewing apparatus of the general type outlined above into which workpieces can be placed easily, quickly and accurately and which can be operated by a worker having minimum skill and training.

Additional objects and advantages of the invention will become apparent from the later following detailed description of preferred embodiments of the invention.

An apparatus in accordance with this invention consists, in brief, of a material-supporting table on which is mounted a work-feeding and guiding mechanism cooperating with a modern high-speed sewing machine preferably of a type equipped with automatically operated stop motion and thread-cutting means. Said work-guiding and feeding mechanism comprises a stationary, horizontally disposed pattern plate or cam track member, a cam track follower cooperating with said cam track member and moveable conveyor means associated with said cam track follower. Said cam track member is formed with a slot constituting the desired pattern of the line of stitching to be sewn, in which slot said cam track follower is moveable. Said conveyor means are arranged for movement relative to the sewing machine and comprise first and second carriage means. The first carriage means is mounted for movement in one coordinate direction on a pair of spaced, first guide rails which are stationary with respect to the sewing machine. The second carriage means is carried by said first carriage means and is adapted for movement in the other coordinate direction. To this end said first carriage means is formed with a pair of spaced, second guide rails arranged orthogonally to said first guide rails. Said second guide rails are adapted to receive, for sliding movement thereon, bearing members rigidly associated with said second carriage means. Thus the combined movement of the two carriage means, each in a different coordinate direction, results in the movement of the whole conveyor means along a curve. Due to the cooperation of the cam track follower with the cam track slot the path of travel resulting from the combined movement of the conveyor means is determined by the shape of the cam track slot.

Although the novel features which are believed to be characteristic of the invention willbe pointed out in the annexed claims, the invention itself as to its objects and advantages and the manner in which it may be carried out may be better understood by reference to the following description taken in connection with the accompanying drawings forming a part hereof, in which:

FIG. 1 is a front view in elevation, certain parts being broken away, of a sewing machine embodying the apparatus for automatic sewing of work material along a preselected, contoured line of stitching;

FIG. 2 is an end view in elevation of the machine shown in FIG. 1;

FIG. 3 is an end view in elevation of the machine shown in FIG. 1 from the other end;

FIG. 4 is a top plan view of the machine shown in FIG. 1;

FIG. 5 is a plan view in section on line 5-5 of FIG. 1;

FIG. 6 is a view in section on line 6-6 of FIG. 4;

FIG. 7 is a view in section on line 7-7 ofFIG. 4;

FIG. 8 is a view in elevation to show the arrangement for rotating one of the windup pulleys for moving the cam follower in its cam slot;

FIG. 9 is an upside down view on line 9-9 of FIG. 8; S-6

FIG. 10 is a rear view in elevation to show certain driving mechanism;

FIG. 11A is a wiring and pneumatic system diagram for automatic control of the machine operation;

FIG. 11B is a wiring'and pneumatic system diagram for automatic control of the operation of the modified form illustrated in FIGS. 12-14;

FIG. 12 is a view in section on line 12-12 ofFIG. 13;

FIG. 13 is a plan view partly in section showing a modification ofthe manner of lifting the work holddown member;

FIG. 14 is a view in section on line 14-14 of FIG. 13;

FIG. 15 is a partial view in elevation of the sewing machine to illustrate a further modification, particularly the holddown cylinder for holding down the holddown plate which is connected to the carriage means;

FIG. 16 is a partial plan view partly in section to illustrate a sight window on the holddown plate and having a slidable shutter member operated by an air cylinder; this view showing the shutter in closed position;

FIG. 17 is a partial plan view, showing the window shutter in open position;

FIG. 18 is a partial view in section on line 18-18 of FIG. 17; and

FIG. 19 is a wiring and pneumatic system diagram for automatic control of the modified construction illustrated in FIGS. 15-18.

Referring now in more detail to the drawings, wherein like reference characters indicate like parts, there is shown a sewing machine 10 which is supported on a table 11 secured to the upper ends of leg members 12. Each of said leg members is formed of two telescopically arranged parts to enable adjustment to suit the particular requirements of the operator of the sewing machine which may be any of the variety of different types of construction. More particularly, the sewing machine may be of the general type shown in U.S. Pat. No. 2,977,9l granted to Covert on Apr. 4, 1961. For insuring that the invention functions in the desired manner, sewing machines of this type and others are available which are equipped with automatic needlepositioning and thread-cutting means, as for example the Union Special Lockstitch machine shown in part in the drawings herein. This machine is sold by Union Special Machine Company of Chicago, Illinois, under the Class 63400 KA or 63400 KB. It will be understood that various types of sewing machines are equipped with automatic needle-positioning and thread-cutting means and these machine types can be used with the invention, so it is deemed unnecessary for present purposes to discuss in detail the associated needlepositioning and thread-cutting means and its automatic control system.

The control system governing the operation of various mechanisms associated with the stop-motion and threadcutting mechanisms of the sewing machine are separate from and independent of the electrical system governing the operation of the work-guiding and feeding mechanism. In a preferred embodiment there is provided, as will be explained later on, an interconnection of the control means for transmitting driving power to the sewing machine and the control means for governing the operation of the work-feeding and guiding mechanism. It will be explained in further detail that both the sewing machine and the work-feeding and guiding mechanism receive driving motion from a common source which is the sewing machine transmitter, and that within the train of connections imparting driving movement to the workfeeding mechanism there is provided means for varying the operational speed of the feeding mechanism by the operator so that the mechanism is capable of changing the feed ratio relative to the stitch ratio and the stitch length may be varied at will.

The machine includes a vertically reciprocating needle 13 in the sewing head, which is driven by conventional mechanism not shown. A pulley handwheel combination 14 is secured to the main drive shaft of the machine 10 and is connected by a belt 15 with a pulley 16 adapted to be driven by a transmitter 17 comprising a motor associated with a stop-motion system including a clutch, a brake and needle-positioning means. Said transmitter 17 may be any one of the standard types which include stop-motion and needle-positioning means and are marketed by various firms, such as, e.g., the American Safety Table Company, Inc. In this type of transmitters the stop-motion and needle-positioning means are controlled by a separate electrical control system which may include a commutator 18. In the present arrangement, as shown, the commutator 18 of a type known in the art, is mounted on the extreme end of the main drive shaft of the sewing machine adjacent the pulley handwheel combination 14. The transmitter 17 is provided with the usual clutch lever arm 19 arranged to bring about engagement of the clutch which drives the pulley 16. Operation of the clutch lever arm 19 is automatic and is instituted by a small single action air cylinder(FlGS. l and 3) which is rigidly mounted onto the clutch lever 19 in such manner that upon actuation of the cylinder the cylinder piston rod 21 will be urged against the transmitter housing thereby biasing the clutch lever 19 away from the transmitter housing into a position-causing engagement of the clutch.

Said pulley 16 is preferably formed with a second groove in which is entrained a second drive belt 23 cooperating with a pulley 24 on a transmission shaft 25. Transmission shaft 25 carries pulley 24 in rigid relation on its outer or left end as best seen in FIG. 3 and is journaled in bearings 26 provided in a pair of brackets 27 depending from and secured to the underface of table 11. At its right-hand end, as seen in FIG. 3, there is secured to the transmission shaft 25 one of a pair of pulleys 28, 29 ofa standard variable pulley drive arrangement such as for example a drive available in the market known as a Var-A-Con Pulley Drive." Pulley drives of this type are available from various manufacturers and, per se, are not part of this invention. Such a pulley drive comprises two pulleys on separate shafts, connected by a V-shaped drive belt such as the belt 30 which is shown as being entrained over pulleys 28 and 29. The two pulleys are provided with split flanges. One flange of each pulley is rigidly mounted to the shaft on which the pulley is carried while the other flange is axially adjustable on the same shaft toward or away from the one flange. In other words, both flanges of each pulley rotate at all times in unison with the rotation of the shaft on which they are carried. Adjustment serves to vary the pitch diameter of the respective pulleys 28, 29, and hence the rotational speed ratio of one pulley to the other. The two flanges are so designed that they incline toward each other in direction of their centers which will explain that movement toward and apart from each other will bring about an increase or decrease of the pitch diameter. As a rule one of the pulleys is provided with spring means for urging the two flanges together, while in the other pulley, manually operable means are used for adjusting the distance between the two flanges. If the flanges of the manually adjustable pulley are urged together, the pitch diameter of that pulley will be increased, increasing the tension in the belt. This will force the flanges of the other pulley further apart against the urge of said built-in spring. From this there will result a change in the driving ratio between the two pulleys, for the pitch diameter of one pulley has increased while the pitch diameter of the other pulley has decreased. The manually operable means for adjustment of the speed ratio may be a screwbolt 31 received in and extending through a threaded hole in a stationary bracket 32. Said screwbolt 31 preferably engages the shiftable flange 28a of the pulley 28 causing it to move toward the stationary flange 28b or allowing it to move away therefrom. In the latter case the normal tension of the drivebelt 30 will cause the shiftable flange 28a to move away from the stationary flange 28b whereby the pitch diameter of the latter will be decreased causing a slacking of the drivebelt. As the tension in the drivebelt is decreased, the shiftable flange 29a of the other pulley 29 yields to the pressure of a spring (not shown) and is thereby shifted toward the stationary flange 29b. This again will bring about a change in the driving ratio. It will now be seen that a rotation of the manual-adjusting means 31 such as said screwbolt will cause a change in the driving ratio between the two pulleys. The present arrangement is provided with a handwheel 31a facilitating rotation of the adjustable screwbolt 31.

In the present arrangement the variable pulley drive comprising pulleys 28, 29 and belt 30, serves to transmit driving motion from the transmission shaft 25 to a speed reduction unit 33 having a speed reduction ratio of preferably 50:1 from input to output. The speed reduction unit is mounted on a suitable bracket 34 depending from the underface of the table 11 in such manner that the input shaft 33:: carrying said pulley 29 extends horizontally while the output shaft 33b extends vertically upwardly. The means for securing bracket 34 to table 11 comprise a plurality of screwbolts 35 cooperating with suitable nuts. These screwbolts extend downwardly through suitable bores in the baseplate 36a of a bearing bracket 36, and through further bores in the table 11 and in said bracket 34. The latter is spaced a small distance below the table 11 by spacer sleeves 37 received on each of the bolts 35. The spacer sleeves serve to provide clearance between said bracket 34 and the underface of table 11, for accommodating therein the downwardly projecting portion of an electric clutch unit 38. Clutch unit 38 is one known in the art. It may be of any suitable standard type. The main portion of the clutch unit is received in an aperture 11a provided in the table 11. Said aperture is open toward the left side of the table as viewed in FIG. 4, giving access to the electrical connectors 38b on the outside wall of the clutch 38. Clutch 38 serves as coupling element between the speed-reduction unit 33 and a sprocket wheel or pulley 40. .There are arranged a pair of vertically disposed shafts 41, 42 in axial alignment with the speedreduction unit output shaft 33b. The major components of the clutch 38 are carried on these two shafts 41, 42 (see FIG. 1). Shaft 41 is rigidly and coaxially secured to the top end of the output shaft 33b of the speed-reduction unit 33. In order to couple these two shafts 33b and 41 together, there is provided a connector sleeve 43 affixed to both shafts at their joining ends. The upper shaft 42 is journaled in a suitable bearing bushing 36b press-fitted into the cylindrical housing 36c of the bearing bracket 36. Shaft 42 is constrained against axial movement in bracket 36, at its upper end by the hub of said pulley or sprocket 40 and at its lower end by the upper driven portion of the clutch 38.

As may further be viewed in FIG. 3, there is provided a stop pin 44 extending downwardly through the face of baseplate 36a of the bearing bracket 36 and engaging a hole or notch in a radially outwardly protruding lobe 36d on the outer housing wall of the clutch 38. This arrangement serves to prevent the outer housing wall from rotation with the coupling element within and thus avoids damage to the electrical components of the clutch.

It is now seen that the clutch unit 38 serves as a coupling member between the train of driving connections extending from transmitter 17 via transmission shaft 25, pulleys 28 and 29, speed-reduction unit 33, shaft 41, said clutch 38 and shaft 42 to the sprocket or pulley member 40. The pulley 40 functions as a windup wheel for a length of chain or cable 52. In this illustrative embodiment the member 40 is a pulley which at a point of its periphery is formed with a notch 50 in which is secured, by means of a connector 51, one end of said cable 52. The other end of cable 52 is secured to a collar 55a of the cam follow member 55. Cam follow member 55 is comprised outside of said collar 55a (see also FIGS. 6 and 7), of a second collar 55b, an antifriction-bearing roller 55d and a shaft 55c on which all of the aforementioned components of the cam follower are rotatably mounted. Cam follower shaft 55c is vertically disposed and secured at its bottom end to one member 97 of the conveyor means later to be discussed.

Referring to FIG. 4, it can be seen that rotation of pulley 40 in counterclockwise direction will cause said cable 52 to be wound up on pulley 40. This in turn will exert a pull on the cam follower 55 and thereby move same along in a cam track slot 56 provided in a cam track plate 57 stationarily mounted on a pair of spaced bracket blocks 58 secured to table 1 1. Said cam track slot 56 is sufficiently wide to allow the cam follower to move freely therein in both directions. Cam track slot 56 is formed in accordance with a desired preselected pattern which-in the case of this embodiment comprises a curved portion 56a and a straight portion 5612. It will be understood that the pattern or contour of the cam track slot 56 may be shaped according to any one of a variable number of lines of stitching that may be desired. Rotation of pulley 40 in counterclockwise direction as seen in FIG. 4 will cause the cam follower 55 to be moved in slot 56 first through the curved portion and then through the straight portion.

It has been found desirable to provide means for varying the starting position of the cam follower 55 in the cam track slot 56 in order to slightly alter the seam pattern. For example, when the curved portion of the seam should become shorter or longer. The starting position is varied in a very simple manner, requiring only an angular adjustment of the starting position of pulley 40. To this end a screw 60 (see FIGS. 1 and 3) is threaded into and through a block 61 depending from and secured to the underface of pulley 40. Rotation in clockwise direction will propel screw 60 further through the block 61 against stop pin 62 extending radially from the cylindrical housing 36c of bearing bracket 36. Depending on the amount of rotation of screw 60, the pulley 40 will be angularly displaced and the block 61 moved toward or away from pin 62. However, such displacement would not insure a definite starting position for the cam follower unless there is provided a force adapted to angularly bias said block 61 in the direction of pin 62. Said biasing force will be discussed later herein. For the present it should be understood that for rotating the pulley 40 in one (counterclockwise) direction, a positive force is applied via said speed reduction unit 33 and clutch 38. For rotating the pulley 40 in the opposed (clockwise) direction a second, positive force is applied. This is a tension force on a cable 66 having a certain pulling force in the direction of a windup pulley 65. This force being herein referred to as counterforce. v

However, the opposing tension or counterforce which is derived from a source later to be discussed, is not sufficiently strong to effectively counteract the first-mentioned positive force on pulley 40, so that pulley 40 will be rotated in counterclockwise direction whenever both forces are applied simultaneously. That is, the driving movement of pulley 40 driven by shaft 41, 42, urging the cam follower 55 to move along from the right to the left as seen in FIG. 4, in the cam track slot 56, is the result of'the differential in forces effective in what is referred to herein as the feeding and counterfeeding directions. From the effect of said counterforce it follows that adjustment of the starting position, of the cam follower 55 in the cam track slot 56, takes place against or by yielding somewhat to said counterforce and before the driving or feed force becomes effective. Adjustment will be brought about by rotating screw 60 in block 61 so as to engage pin 62. This will rotate pulley 40 against said counterforce. The pulley 40 will yield to the counterforce whereby, via cable 52, the cam follower 55 will be positioned in slot 56 in the adjusted and desired place for starting a sewing cycle operation.

The opposing counterforce which is herein referred to as the counterfeed force as against the feed force imparted to pulley 40 via clutch 38, is permanently effective which, in turn, means that as long as no feed force is applied on pulley 40, the latter will be urged by the counterfeed force (i.e., the pull on cable 66 toward pulley 65) to stop against pin 62.

The source of the counterfeed force is a double-action, high-pressure air cylinder 78 (see FIGS. 1, 2, 4, 8, 9) having an intake port and an outlet port 81. Actuation of said air cylinder results in actuation of a mechanism adapted to rotate second driving pulley 65 on the periphery of which is fastened a cable 66 in the manner in which cable 52 is fastened to pulley 40. Windup direction of pulley 65 may be clockwise or counterclockwise. However, in the present arrangement windup direction of pulley 65 is clockwise, as viewed in FIG. 4. Pulley 65 is rigidly mounted on a vertically disposed rotatable shaft 67 journaled in bearings 68, 69. Bearing 68 is secured to the top surface of table 11 by suitable screw means while bearing 69 is affixed in a similar manner to the underface of the table 11. Shaft 67 is constrained against axial movement in said bearings 68, 69, at its upper end by the hub portion of pulley 65, and at its lower end by the hub portion of a pinion or gearwheel 75 rigidly fastened to the lower end of shaft 67. Gearwheel 75 is arranged to cooperate with a gear rack 76 secured to the free end of the piston rod 77 of said double-action air cylinder 78. Air cylinder 78 is rigidly secured in a bracket 79 affixed to the underface of table II. The air cylinder 78 is constantly charged with high-pressure air causing the piston rod 77 to be normally urged into an extended position (see also FIGS. 9 and 10). For insuring a smooth operation of the air cylinder there are provided at its intake port 80, and outlet port 81, airflow control valves 82 and 83. Valve 82 serves to regulate the flow of high-pressure air through port 80. Valve 83 regulates the exhaust air to the atmosphere through port 81. Now it will be seen that air cylinder 78 urges pulley 65 to rotate clockwise, thus causing a pulling force on cable 66 which is trained over idler guide pulley one end of the cable being anchored to cam follower 55 and the other end to the periphery of windup pulley 65.

During the feeding (sewing) phase of the operation cycle, the piston rod is forced back into air cylinder 78. Since the latter is under constant pressure by compressed air supplied through intake port 80 (shown at the left of the air cylinder 78 in FIG, 8), the retracting movement of the piston rod 77 will move the piston against the intake port 80 whereby the pres sure on that side of the piston will build up heavily. This pressure could increase so much as to cause stalling of the retracting movement of the piston rod which in turn would mean that rotation of gearwheel 75, shaft 67 and pulley 65 would be halted causing interruption of the feeding (sewing) phase. An occurrence of that sort would defeat the automatic function of the apparatus. In order to prevent this, there is provided, in the air line 84, between intake port 80 and the pressure flow control valve 82, an adjustable pressure-relief valve 85 of any suitable standard type.

The arrangement of valve 83 at the exhaust port 81 of the air cylinder 78 serves as one of two means for insuring a smooth return of the cam tract follower and the carriage means associated therewith, after completion of the sewing cycle. The second means for controlling the return movement is a controlled slight engagement of clutch 38 to be discussed later on.

Viewing FIGS. 1-4, it can be seen that the guiding and feed ing mechanism extends generally transversely of the arm of the sewing machine, i.e., it extends in normal feeding direction which makes it possible to feed the work through the stitchforming zone of the sewing machine in nearly the same fashion as this would be done by an operator guiding the work manually under the needle.

Referring now to the construction and function of the work conveyor means and the guide rail means associated therewith, there are a pair of transversely spaced guide rails or rods 90 which are fixedly secured at their opposite ends in suitable bores in spaced blocks 58 (see FIGS. 14), Received for sliding movement on each of guide rails 90 are a pair of spaced blocks 91. Each of the two blocks 91 on each guide rail is laterally aligned with one another, block 91 on the opposite guide rail 90. Thus the four slide blocks 91 are arranged in fixed rectangular relation in which they are maintained by plate 92. Plate 92 is mounted on top of these four blocks in such manner that each block supports the plate on one of its four corners. Between each of the two opposite blocks 91 on guide rails 90 there extends a further guide rail 93. Guide rails 93, blocks 91 and plate 92 form together a carriage 94 adapted for sliding movement along guide rails 90. To this end, blocks 91 are provided with bearing bushings 95 for facilitating sliding movement on rails 90. The secondary guide rails 93 are received at their opposite ends in rigid manner, for example, by screw means in suitable bores in blocks 91 and carry each a pair of spaced, slidable blocks 96. Said blocks 96 are provided with bearing bushings too, for facilitating sliding movement on rails 93. Each block on each guide rail is aligned with one block on the opposite guide rail; all four blocks forming a generally rectangular pattern. They are interconnected by a pair of plates 97 and 98. Plate 97 is mounted on top of the blocks and plate 98 is mounted on their bottom side (FIG. 7). The mounting means may be screws. Blocks 96, plates 97 and 98 form together a second carriage 100 which is movable perpendicularly to the direction of the movement of the carriage 94. It will now be understood that carriage 94 is movable in one coordinate direction and carriage 100 in a second coordinate direction. Carriage 100 is so arranged relative to carriage 94 that its top plate 97 is disposed in a plane above upper plate 92 of carriage 94, while its bottom plate 98 is disposed in a plane below the plate 92. Plate 97 serves as the support base for shaft 55c of cam follower 55. Shaft 550 may, for example, be formed at its bottom end with a reduced diameter portion having a thread thereon which extends through a hole provided in plate 97. A nut threaded onto said reduced diameter portion of shaft 55c frame underneath the plate 97 rigidly secures the shaft to the plate 97 (see FIG. 6). For the purpose of enabling the cam follower to move in the direction of guide rails 93 along with the movement of carriage 100 without interfering with carriage 94, there is provided a transversely extending slot 101 in plate 92 of carriage 94.

FIGS. 5 and 6 are sectional views disclosing the arrangement of the coordinate guide rail system andthe mounting means for the work engagement means. When viewing these two figures it can be seen that there is provided a longitudinally extending hinge means 105, one hinge butt portion 105a of which is secured by suitable screw members to the top surface of the bottom plate 98 of carriage 100. F astened to the other hinge butt portion 105b is an intermediate plate 106 which extends forwardly of said hinge means as best seen in FIG. 5, or toward the left as best seen in FIG. 6. At its forward end there is mounted to the bottom surface of plate 106 the work holddown high-friction 107. Plate 107 is of a heavier gauge than plates 106 or 98 and, due to gravity, serves in conjunction with a pair of parallel strips 108 made of a high-fric tion material, such as rubber or other suitable material having a high coefficient of friction, as the friction and pressure-imparting means for holding down and guiding the workpiece to and through the stitch-forming zone; the workpiece being shown diagrammatically at W. As shown in FIG. 5, the work holddown plate 107 is provided with a slot 112 having a straight and a curved portion. Slot 112 accurately corresponds to the shape of the desired seam and serves to permit passage of the needle through the plate 107 when said plate is moving under the needle as a result of the combined movement of carriages 94 and 100. The two strips 108 are affixed, preferably by an adhesive to the underside of the work holddown plate 107, in parallelism with and at both sides of slot 112. In contrast to the high-friction material 108, the work-supporting table top is covered with a sheet or layer 113 of material having an extremely low-friction coefficient, such as highpolished metal, Teflon or Mylar. As earlier explained this provides for a friction differential by which the work W will be moved to and through the stitch-forming zone. It will be noted that the pressure foot and feed-dog means of the conventional sewing machine are eliminated.

It is now seen that the work holddown plate 107 functions on the gravity principal so that no means for employing pressure from above, such as the conventional pressure foot of conventional sewing machines, is necessary. Raising the plate is a different matter and to this end there is provided an air motor 115 in the form of an air cylinder having a piston (not shown) received therein and a piston rod 115a extending upwardly from the air cylinder; the piston rod terminating in a plastic cap 115b. Air cylinder 115 is mounted to the undersurface of the table 11, by means of a bracket 116, so that the piston rod 115a when extended, will engage from below the work holddown plate 107 and swing same upwardly about the axis of hinge 105, permitting insertion or removal of the work. More details regarding the operation of air motor 115 and the means for controlling this operation will be described later under the heading CONTROL SYSTEM AND OPERA- TION. Springs on studs 111 may be added as shown in FIG. 7 if more pressure on plate 107 is required. The work-engaging plate 107 is shown as being further formed with a number of perforations 117 (see FIGS, 4 and 5), through which is visible on the work-supporting surface 113 a colored guideline 118, preferably white. The perforations 117 serve mainly to allow the operator to visually control his manual alignment of the work with said guideline 118, before he starts the automatic mechanism.

As shown in FIGS. 4, 6 and 7, there is provided means for insuring that the cam follower 55 is properly propelled along the cam track slot 56 at a uniform speed. This is of particular importance since the cam follower has to be moved first through a curved portion of the slot 56, which extends substantially perpendicularly to the direction in which the driving pulley 40 is located. It will be remembered that a chain or cable 52 is utilized for propelling the cam follower 55 along the cam track 56. However, the cable 52 should travel on the centerline of the slot 56 without cutting across the corner formed by the curved portion of the slot. This travelling of the cable across the corner should not be allowed, for the simple reason that it would cause an intermediate change of the stitch length. The explanation for such an undesired change of the stitch length is that the distance around the curve would be negotiated by the cam follower 55 in a shorter time than an equal distance of the straight portion following thereafter if the cable is allowed to cut across and not be in line with the path of travel of the cam follower. That, of course, would upset the relation between speed of the work and needle speed. The result would be that around the curve the stitches would become longer than on the straight portion of the cam slot 56. Further, the pull of the cable could become too steep, i.e., too perpendicular relative to the directional disposition of the slot 56 at its starting end, and this might cause the cam track follower to bind in the slot.

The above-mentioned means for insuring that the cable travels the path of the cam slot, comprise a guide pulley 120 which is rotatably mounted on a shaft 121 (see FIG. 7) oriented in concentric relation with the curved portion 56a of the cam track slot 56. Shaft 121 may be a shoulder screw threaded into a suitable hole in the cam track plate member 57. Further, shaft 121 is formed at its upper end with a threaded bore in which is received the threaded portion of a second shoulder-screw-type shaft 121a.

Pulley 120 serves as a means for guiding the cable 52 along the curved portion of slot 56 on exactly the centerline of the latter. In order to enable cable 52 to be entrained in the groove of pulley 120, the latter is formed on its periphery with a halfway completed segmental cutout 120a, which serves as clearance for cam follower 55. Without this cutout, pulley 120 would overextend slot 56 and interfere with follower 55. Due to the not complete segmental shape of cutout 120a, the latter forms, at its incomplete side, a flat, radially extending edge or nose 12% which may be enlarged radially outwardly as shown in FIG. 4.

Referring to FIGS. 6 and 7, it will be noted that pulley 120 is coplanar with collar 55a and that a pair of guide pulleys 122 and 125 are coplanar with collar 55b of cam follower 55. This insures that the cables 52 and 66, which are fastened to collars 55a and 55b will be guided in the correct planes. To this end it should be understood that pulley 122 is mounted on the shoulder screw shaft 121a and thus is automatically concentric with pulley 120. Pulley 125 is mounted on a shaft 126 screwed into a suitably threaded bore in cam track plate member 57. The location of pulley 125 is, of course, such that it guides the cable 66 substantially on a tangential line relative to the curve of slot 56 at the starting end thereof. Low-friction washers 127, 128 may be provided on shafts 121, 121a and 126 at the bottom and top sides of pulleys 120, 122 and 125 to insure rotatability of the latter on said shafts. Also, it will be noted that the pitch diameter of the pulley 122 does not coincide with the pitch diameter of pulley 120. The reason is, that pulley 122 serves to guide only cable 66 when cam follower 55 moves along slot 56. It is not critical whether or not cable 66 cuts across corners. It is significant to note here that the arrangement as described above may be utilized for a plurality of curves in the cam track slot if a multicurved seam, such as in pocket-stitching, is required. This is, the invention provides means for automatically sewing a line of stitching of an almost infinite variety of preselected contours or curved lines of stitching by providing a correspondingly shaped cam slot in plate 57.

In operation in feed direction, the pulley 120 will stop with its nose 12% against a magnetic stopblock 129 mounted on cam slot plate 57 and positioned adjacent slot 56, and will be retained thereagainst until cam follower 55 reengages it on its way back on the return cycle. The stopblock 129 is mounted at the junction of the curved and the straight portion of slot 56. This arrangement prevents the pulley 120 from further rotation whereby its larger radius portion could move over the cam track slot and thus be in the way of the follower when the follower is retracted after the conclusion of the sewing operation.

In a suitable location on the underface of the table board 11, there is mounted a bracket (FIGS. 1 and 2) carrying a pair of switch means S-3 and 8-4 adapted to be alternately engaged by an arm 131 pivotally mounted at 131a on said bracket 130. In this arrangement the pivotal arm 131 is normally biased upwardly by a spring 132 and thus normally engages switch S-3. Spring 132 is fastened at one end to a screw 133 threaded into the free end of said pivotal arm and at its other end to a downwardly turned portion of bracket 130. Rotation of said screw 133 in arm 131 will adjust the tension of spring 132. Also there are provided a pair of stop pins 134, 134a for restricting the pivotal movement of arm 131 so as to protect switches S-3 and S-4 against damage by overactuation of arm 131. Actuation of arm 131 against the force of spring 132 is achieved by operating a treadle 135. The treadle is connected with arm 131 by rod means 136. The upper end of rod 136 is connected to the outer free end of pivoted arm 131 by means of a clevis 136a.

In the arrangement, as shown, there is a further switch 8-2 which is mounted for engagement by carriage 94 when same is in stopping position; that is, at the end of the stitch-sewing movement. To this end, switch 8-2 is mounted on the table top is such manner that its actuating trigger arm is interposed for displacement in the path of movement of the carriage 94.

An air cylinder 140 is mounted in suitable bracket means 139, preferably secured to the head cover of the sewing machine. As best seen in FIGS. 1, 2 and 3, said air cylinder is so arranged that its extended piston rod 140a, which is provided at its free end with a plastic button or head 141, will engage the work-engaging plate 107 in the immediate vicinity of the needle 13. Mounting of the air cylinder, at an angle as shown, is desirable in order to enable piston rod 140a, when extended, to engage plate 107 in close proximity of the needle. Further, there is provide photoelectric-sensing means comprising a light-sensitive cell which, as shown, is a Hoffman solar cell and a light source 142. Solar cell 145 is accommodated and secured in a bore in table 11. The location of the Solar cell 145 see FIG. 6) is such that it will lie in line with the straight portion of the slot 112 in the work-engaging plate 107 during the last phase of the sewing operation, that is, during the straight-sewing portion of the operation. Thus, when the workpiece passes over and beyond the Solar cell, the light-sensitive cell will be exposed to a beam of light emitted by said light source 142. Light source 142 is mounted in a suitable position preferably on a bracket 143 secured to the sewing machine 10.

CONTROL SYSTEM AND OPERATION For the purpose of explaining the various details of the control system of the apparatus herein disclosed, a typical cycle of an automatic-seaming operation including the preceding and successive stages of the latter, will be described.

In the drawings, and more particularly in FIGS. 1 and 4, there is outlined a desirable location of a control box C13 in which are contained most of the electrical and pneumatic components.

During the previous discussion of the construction details of the apparatus, various air motors have been referred to and in particular control means connected with air motor 78. Also described is the arrangement of several electrical switch means including a photoelectric means, and in conjunction therewith, means for operating these switch means. Hereinafter, reference will be made to the various pneumatic and electrical devices in connection with the wiring diagrams for explaining the functioning of the control system.

The control system comprises, in general terms, fluid actuated means and electrical means. The fluid means may be any type of suitable fluid means utilizing liquid or gaseous fluid. However, high-pressure air is preferred since it is clean, more readily available than other fluids and does not require closed line circuits. Both the fluid and the electrical control systems are partially interconnected with one another. The connections reside in the integration of the electrical circuits controlling air valves 155 and 160 in the overall electrical circuitry making up the control system of the apparatus.

For a better understanding of the two control systems, reference is now made to FIG. 11A of the appended drawings.

1. CONDITION OF APPARATUS AND CONTROL SYSTEM BEFORE COMMENCEMENT OF THE OPERATION CYCLE l. A complete operation cycle is composed of the following phases:

Work engagement by the holddown member 107.

Starting of the conveyor means.

Starting of the sewing machine simultaneously with starting of the conveyor means.

Performing of the sewing operation.

Stopping of the sewing operation after completion of the seam.

Returning of the work holddown member to its starting position.

Lifting of the work holddown member 107, to permit removal of the stitched workpiece.

In a later-to-be-discussed, alternate arrangement, a slight change in the sequence of phases of the sewing cycle will take place in that the work holddown member will disengage immediately after completion of the sewing operation and before it is returned to its starting position.

2. Turning now to the prestarting state of the fluid control system, it will be understood that high-pressure air is received from a suitable source through a main supply line 150 via a filter regulator lubricator unit 151. From here high-pressure air will be introduced into lines 84, 152 and 153. Line 84 is connected with said air motor or air cylinder 78 via the airflow control valve 82 and intake port 80 of cylinder 78. As previously described, a second control valve 83 is connected to the exhaust port 81 of the air cylinder 78. Also there is arranged a relief valve 85 between airflow control valve 82 and intake port 80. The function of cylinder 78 and the valves associated therewith have been described. Line 152 extends from main supply line 150 to a solenoid-controlled three-way valve 155 having an intake port 155a, an outlet port 155b, and an exhaust port 1550. The outlet port 155b is connected by a line 156 via an air pressure regulating valve 157 with the intake port of the single-action holddown cylinder 140. A branch line 156a extending from line 156 between port 155b of valve 155 and pressure-regulating valve 157, serves to supply high-pressure air to the clutch-engaging cylinder 20 via a flow control valve 158. The third line 153 extending from supply line 150 leads via a pressure-regulating valve 161 to the intake port 1600 of another three-way solenoid-controlled valve 160 having said intake port 160a, an outlet port 160b, and an exhaust port 1600. The outlet port 16% is connected via air line 162 with the intake port of said air cylinder 115 serving to lift the work engagement plate at the completion of the operation cycle.

3. Turning now to the electric circuit system as diagrammed in FIG. 11A, large block dots indicate hot terminals, while three short horizontally extending lines disposed one below the other, indicate ground terminals. There is a main hot terminal denoted HT and a main ground terminal denoted GT. In the electric diagram there are also shown a number of subter' minals. This showing serves explanatory purposes only. In reality all subterminals are connected to the respective one of the main terminals HT and GT. Main terminals HT and GT are in turn connected to a source of 1 v., 60-cycle alternating current (AC). All subterminals are denoted by the letters T" or GT" plus a suffix letter of number, as for example, T-l for a hot subterminal and GT-l for a ground subterminal.

A. If power is turned on by a main switch 8-1, the light source 142 will be energized emitting a beam of light in downward direction where the light-sensitive Solar cell 145 is located.

aa. Actuation of the main switch will further close a circuit l-IT-GTT-l extending via the primary coil of a transformer 171. The transformer here used is preferably of the type providing for an output of 18 v. and 20 v. from its secondary coil.

bb. Connected to the 18 v. output of transformer 17! is a powerline extending to a contact R4-1 of a relay R4. Contact R4-1, at this preoperation phase, is closed and completes an 18 v. circuit extending from the secondary coil of the transformer 171 over a standard power pack 174 to a ground terminal RT-! 1. The powerpack 174 serves as a DC converter, converting alternating current into direct current. It operates the clutch 38 by energizing the field coil 38a thereof which is switched across the powerpack terminals 3 and 4. In the standard powerpack here under consideration the voltage output between terminals 3 and 4 depends on the voltage input through its terminal 2. An input of 18 v. AC will produce an output of approximately I? v. DC for energizing field coil 380. This will provide the effective slippage of clutch 38 which serves on one hand, to hold the cable 52 under a slight tension and therefore keep it straight and prevents buckling, and on the other hand, to act as a sort of slowdown factor against the return movement of the conveyor means (carriages 94 and 1100) upon completion of the stitching operation.

The line 177 extending between terminals 3 and 7 of the powerpack represents an external wire as required by the standard powerpack circuitry.

C. At this point it will also be noted that a circuit extending from terminal T7 to terminal GT9 via a variable resistor 182, a rectifier 183 and contact R5-2 of a relay R5, is closed-energizing relay R4 (this implies that a relay R5 is not energized as will be explained).

D. Normally closed switch S-2 mounted on the table top in the rear of the work-feeding and guiding mechanism is engaged by the carriage 94 as same is at its utmost righthand position (starting position). Switch 8-2 is held open by carriage 94.

E. Normally closed switch 8-?! mounted in the top position on bracket is engaged by a pivot arm 131 and held open thereby.

F. Normally open switch S-4 located in the lower position on bracket 130 is not engaged by said pivot arm 131 and is therefore held open too.

G. The Solar cell is arranged in a preconstructed and known circuitry (here a Hoffman circuitry) adapted to energize the coil of relay R3 upon exposure of the Solar cell to light. Since the circuitry associated with the Solar cell is standard, it is believed to be unnecessary to enter into details concerning it. In the present state, preceding the operation cycle of the apparatus, the Solar cell is not exposed to the light beam emitted from said source 142 as the work-engaging plate 107 has been moved over the Solar cell covering it. As mentioned above, the operation of the Solar cell is set on light operation so that relay R3 is now deenergized. This causes relay contact 113-1 to be closed. However, it will been seen from FIG. 11A that at this stage no circuit extending over relay contact R3-l is completed.

4. As a result of the situation outlined under Item 3 above, the relays R1, R2, R3 and R5 are all deenergized while relay R4 is energized. This means:

A. No current is conducted to the solenoid of valve 160 because:

aa. contact Rl-ll of relay R1, as well as switch 8-3, are

both open.

bb. contact R2-3 of relay R2 and contact R5-1 of relay R5 are also open.

B. No current is conducted to the solenoid of valve for the reason that contacts R2-3 and R5-1 of the deenergized relays R2 and R5 are still open.

C. The electric clutch unit 38 (see FIG. 3) is still operating on a 17 v. DC current as explained under 3B-bb.

5. A circuit extending from Terminal T4 to terminal GT6 via terminals 1 and 8 of timing unit 175 is established. At present, this is without influence on the setting of the timer unit. However, circuit T4-GT6 has caused an interruption between terminals 2 and 3 of the timing unit 175, at the end of the preceding operation cycle.

6. SUMMARY The apparatus is now ready for commencing a new operation cycle. The work holddown member 107 is raised by the air cylinder 115 due to the fact that the circuit for energizing the solenoid valve 160 is still interrupted so that valve 160 is open permitting high-pressure air to flow from line 153 through line 162 to air cylinder 115. The sewing machine is in stop position as the cylinder adapted to operate the clutch lever 19 is not actuated as yet, since valve 155 is closed due to the deenergization of its solenoid, which in turn stems from the fact that no current is conducted therethrough. Clutch 38 is operating on only 17 v., which can do no more than bring about said slippage engagement which is sufficiently weak that it is easily overpowered by the torque that is effective on pulley 65 and causes the pulley to wind up on its periphery cable 66 and thereby retain the conveyor means in starting position. The Solar cell 145 is, as has been mentioned before, darkened. This causes relay R3 to be deenergized so that contact R3-1 is closed. Contact R3-1 is connected with the coil of relay R2. Relay R2 cannot be energized before the closing of switch S-4 has been effected, and this switch has not as yet been closed. The work W that is to be stitched, is now introduced under the work-engaging plate 107 manually by the operator.

II. OPERATION l. The operator starts the apparatus by closing switch 8-3. in the arrangement, as shown, the treadle 135 is connected with the free end of pivot arm 131 for actuating switches S-3 and 8-4. The operator depresses the treadle causing the pivotable arm 131 to be disengaged from the normally closed switch 8-3.

A. This closes a circuit from T3 to GT2 via switch S-3 and the coil of relay R1. B. Further, a circuit T3 to GT4 over the coil of solenoid valve 160 is momentarily (as long as the treadle is being depressed) established. This energizes the solenoid coil thereby closing port 16017 of valve 160 and shutting off the flow of high-pressure air to cylinder 115. As a result, the holddown member 107 drops down upon the work by means of gravity, the operator having placed the work W in proper position on the surface of table 11 under the holddown member. As mentioned before, the holddown member may be spring-pressed by springs 110, if desired. 2. Switch S-4, which is of the normally open type, is closed immediately after the closing of switch 8-3 by the operator, who for this purpose depresses the rod 136 by the treadle 135.

A. This establishes a circuit extending from T5 via switch 5-4, the coil of relay R2 and closed contact R3-1 to GT-3. This circuit now energizes relay R2. B. Energization of relay R2 causes closing of contacts R2-1 and R2-3; it also causes opening of contact R2-2. C. Opening of contact R2-2 interrupts circuit T4-GT6 via timer contacts 1 and 8. This resets the timer 175, i.e., restores the connection between the timer contacts 2 and 3. (See I, 5 D. Closing of contact R2-3 establishes:

aa. A circuit extending from T4 to GT7 over the coil of relay R5 and contacts 2 and 3 of the timer 175, energizing said relay R5.

bb. A circuit extending from T4 to GT8 via the solenoid of valve 155, energizing said solenoid. This opens valve 155 and establishes an air passage from line 152 to lines 156, 156a with the result that air cylinders 140 and 20 are actuated. Speed control valve 158 in line 156, 156a provides, in this phase of the operation, a slight delay to allow a 300 mf. capacitor 180 which is switched across the coil of relay R4, to discharge through a 300-ohm resistor 181. Resistor 181 is connected to a ground terminal GT10. The discharge of capacitor 180 takes place further through the coil of relay R4. It is understood that the delay is therefore very brief. (Reference to ll, 2, E, cc).

cc. A circuit from T4 to GT4 over the closed contact R5-1 of relay R5 (refer to II, 2, E, aa). Circuit T4-GT4 is one of two holding circuits for keeping the solenoid of valve energized during the operation cycle. Cylinder 115 is thereby maintained in inactive state. (For the second holding circuit, refer to item ll, 4, A).

dd. A first holding circuit for energizing relay R1 extending from T4 to GT2 via contact R2-3 of relay R2 contact R5-1 of relay R5 (refer to Item 11, 2, E, aa) and coil of relay R1. (As will be explained in Item 11, 4, A, there will be a second holding circuit from T2 to GT2).

E. Energization of relay R5 (refer to Item ll, 2, D, aa)

causes closing of contacts RS-l and R5-3. It also causes opening of contact R5-2.

aa. As a result of closing contact R5-l, said circuit T4 to GT4 (refer to Item 11, 2, D, cc) and said circuit T4-GT2 (refer to Item ll, 2, D, dd) are established.

bb. As a result of the opening of contact R5-2, said circuit T7 to GT9 via resistor 182, rectifier 183, the coil of relay R4 and capacitor is interrupted causing deenergization of relay R4. The deenergization of relay R4 is slightly delayed by the discharge of capacitor 180 via coil of relay R4 and resistor 181. (See next item.)

cc. As a result of closing contact R5-3 the capacitor discharge time is sped up in that said resistor (300- ohm) 181 is now connected with capacitor 180. It has already been explained that resistor 181 is connected with a ground terminal GT10 (refer to Item II, 2, D, bb).

F. Deenergization of relay R4 (refer to Item II, 2, E, bb)

opens contact R4-1 and closes contact R4-2.

aa. Opening of contact R4-1 interrupts said 18 v. circuit extending from transformer 171 to GTll (refer to Item I, 3, B, bb).

bb. Closing of contact R4-2 establishes a circuit T8 to GTll. This circuit is almost like the circuit described under Item I, 3, B, bb. The voltage input to the power pack 174 through this circuit is 110 v., 60-cycle AC. The powerpack acts as a DC converter putting out about 90 v. DC for energizing the field coil 38a of clutch 38, which is switched across powerpack terminals 3 and 4.

cc. This will now cause the electric clutch 38 to fully engage. The transmitter clutch is now being engaged (see next item dd) to provide the necessary torque for rotating pulley 40 in counterclockwise direction against the counterfeed force supplied by air cylinder 78. The con veyor means comprising carriages 94 and 100, together with the work-engaging holddown plate 107, will now commence to move in a substantially two-coordinate direction through the first part of the forward stroke of the sewing cycle. It will be understood from the earlier discussion, that the direction or path of movement of the conveyor means is predetermined by the configuration of the cam track slot 56, in which cam follower 55 is mounted for movement therein.

dd. Simultaneously, the time delay caused by the adjustable airflow control valve 158 (refer to Item ll, 2, D, bb) has elapsed and enough pressure has built up in cylinder 20 to operate the transmitter clutch lever 19 and cause the transmitter clutch to engage. This starts the sewing operation.

3. It will now be understood that as soon as the switches S-3 and 8-4 are closed, a number of holding circuits are established. These holding circuits in turn allow the reopening of the switches S-3 and 8-4 without causing any changes in 

1. Apparatus for guiding work to be stitched along a predetermined path through the stitching zone of a sewing machine, said machine having a reciprocating needle in said stitching zone, which apparatus comprises a table having a stationary work-supporting surface; a pattern plate; means mounting said pattern plate in a stationary, fixed position on said table; a cam slot in said pattern plate shaped to the contour of the seam to be stitched in said work; a follower member movable along and guided by said cam slot; means connected with said follower member to cause said follower member to travel along said cam slot; said means comprising power-operated first drive means for moving the follower member during the sewing operation from a starting position to an end position in synchronization with the operation of the sewing machine and power-operated second drive means for returning the follower to the starting position after termination of the sewing operation, the second drive means being operable independently of both the first drive means and the sewing machine; first carriage means operatively connected with said follower member and movable in one coordinate direction in response to the movement of said follower member; second carriage means operatively connected with said first carriage means and movable in another coordinate direction in response to the movement of said cam follower member whereby said first carriage means is also moved in the other coordinate direction; guide means associated with each of said carriages for guiding the movement of each carriage in its coordinate direction; and work holddown means positioned above and adjacent to the work-supporting surface of said table, said holddown means being operatively connected to said first carriage means; the combined movement of said carriages in response to movement of said follower member causing said work holddown means to move said work on said table surface through said stitching zone in a path defined by said contour of Said cam slot so that said needle sews a seam in the work having the same contour as the contour of the cam slot of the pattern plate.
 2. Apparatus according to claim 1 wherein the first drive means comprises first windup means having a vertically disposed shaft, a speed reducer having input and output shafts, a power-driven rotatable shaft, a variable speed drive connecting said power-driven rotatable shaft and said speed reducer input shaft, a clutch connecting said speed reducer output shaft and the shaft of said first windup means; a first elongate flexible means connected at one end to said first windup means and at its other end to said follower member; and said second drive means comprises second windup means having a vertically disposed shaft; a pressure fluid cylinder means exerting a yieldable torque on said second windup means; a second elongate flexible means secured at one end to said second windup means and at its other end to said follower member; and means guiding said first flexible means in a vertical plane coincident with a vertical plane through the length of said slot.
 3. Apparatus according to claim 1 wherein said first drive means comprises first windup means having a vertically disposed shaft, a speed reducer having input and output shafts, a power-driven rotatable shaft, a variable speed drive connecting said power-driven rotatable shaft and said speed reducer input shaft, a clutch connecting said speed reducer output shaft and the shaft of said first windup means; first elongate flexible means for moving said follower member in said cam slot, said first flexible means being secured at one end to said first windup means and at its other end to said follower member; and said second drive means comprises second windup means having a vertically disposed shaft, power means exerting a yieldable torque on said shaft of said second windup means; second elongate flexible means for moving said follower member in said cam slot, said second flexible means being secured at one end to said second windup means and at its other end to said follower member, and means guiding said first flexible means for moving said follower member in said cam slot.
 4. An apparatus according to claim 3 in which the cam slot in said pattern plate has a straight portion and a curved portion, said elongate flexible means comprise cable means, said first and second windup means comprise pulleys mounted on vertically disposed shafts, and said guide means comprise pulleys mounted on vertically disposed shafts and over which said cable means are trained.
 5. An apparatus for guiding work to be stitched along a predetermined path through the stitching zone of a sewing machine, said machine having a reciprocating needle in said stitching zone, which work-guiding apparatus comprises a table having a surface which has a low coefficient of friction on which the work to be stitched is slidable; a horizontally disposed pattern plate; means mounting said pattern plate in stationary fixed position above said table; a cam track slot in said pattern plate shaped to the contour of the seam to be stitched in said work; a cam track follower movable along and guided by said cam track slot from a starting position in a forward stroke to a stopping position and in a retraction stroke back to said starting position; a first rotatable windup pulley above said table surface having a vertically disposed rotatable shaft fixed thereto and extending downwardly through said table; a speed reducer having a rotatable input shaft and a rotatable output shaft, the output shaft being connected to said first windup pulley shaft; a prime mover comprising a sewing machine transmitter means mounted under said table and having a drive shaft; motion-transmitting means connecting said transmitter drive shaft and the input shaft of said speed reducer; clutch means connecting the output shaft of said speed reducer and the downwardly extending shaft of said first windup pulley for rotating said first windup pulley; a first cAble connected at one end with said cam track follower to travel therewith and connected at its other end to the periphery of said first windup pulley, said first windup pulley when rotated in one angular direction causing said cam follower to travel along said cam track slot in a forward stroke from said starting position to said stopping position; a second rotatable windup pulley above said table surface having a vertically disposed, rotatable shaft fixed thereto and extending downwardly through said table; a second cable connected at one end to said cam track follower to travel therewith and connected at its other end to the periphery of said second windup pulley, said second windup pulley, when rotated in one angular direction, causing said cam track follower to travel along said cam track slot in a retraction stroke from said stopping position to said starting position; a yieldable torque-exerting means connected to the shaft of said second windup pulley exerting a torque on said windup pulley shaft, to rotate said second windup pulley; a first carriage means movable in one coordinate direction and operatively connected with said cam track follower and movable in that coordinate direction in response to movement of said cam track follower in said cam track slot; a second carriage means movable in another coordinate direction and operatively connected with said cam track follower and movable in said other coordinate direction in response to movement of said cam track follower in said cam track slot; guide means mounting each of said carriages for slidable movement of each carriage in its coordinate direction and said first carriage means in said other coordinate direction as well; a work holddown means operatively connected to one of said carriages and positioned adjacent the surface of said table, and movable toward and away from said surface for releasably clamping the work under said holddown means for slidable movement of the work on said surface through the sewing zone of the sewing machine; the combined movement of said carriages in response to movement of said cam track follower causing the work holddown means and the work clamped under said holddown means to move on said table surface through said stitching zone in a path which has the same contour as the contour of said cam track, so that said needle sews a seam in the work having the same contour as the contour of said cam track of the pattern plate.
 6. Apparatus according to claim 5, wherein the motion-transmitting means connecting the transmitter drive shaft and the input shaft of said speed reducer comprises a belt-driven rotatable shaft driven by said transmitter drive shaft, a first two-part pulley fixed to said belt-driven rotatable shaft, the pitch of which is adjustably variable, a second two-part pulley fixed to said speed reducer input shaft, the pitch of which is adjustably variable and a belt trained over said two pitch-adjustable pulleys and means operable to adjust the pitches of said two pulleys to control the speed ratio of said first two-part pulley to said second two-part pulley.
 7. Apparatus according to claim 6, in which said clutch means is operable selectively in a first position to partially engage in a manner that provides a slippage engagement whereby the torque on said first windup pulley shaft is less than the torque exerted by the torque-exerting means connected with the shaft of said second windup pulley and to a second position to fully engage in a manner that provides a torque on said first windup pulley shaft greater than the torque exerted by the torque-exerting means connected with said second windup pulley shaft.
 8. Apparatus according to claim 7, in which the means-exerting torque on said second windup pulley shaft comprises a compressed air cylinder having a reciprocating piston which has a gear rack secured thereto, said gear rack meshing with a gearwheel secured to said second windup pulley shaft, the compressed air cylinder having valve and port means providing a yieldaBle torque force on said second windup pulley.
 9. Apparatus according to claim 5, in which the first carriage means and said guide means comprise four slide blocks arranged in rectangular orientation, a plate resting on and secured to said blocks, a first pair of said blocks being slidable on one of a pair of oppositely disposed parallel guide rails and a second pair of said blocks being slidable on the other of said pair of guide rails, said pair of guide rails being fixedly mounted at each end on a pair of oppositely disposed supporting blocks secured to said table, the second carriage means comprising four second carriage slide blocks arranged in rectangular orientation, an upper plate resting on and secured to said four second carriage slide blocks, one pair of said second carriage slide blocks being mounted for slidable movement on one of a pair of parallel second carriage guide rails and the other pair being mounted for slidable movement on the other of said pair of second carriage guide rails, said second carriage guide rails being secured at their ends to said slide blocks of said first carriage, a lower plate secured to the bottom sides of said second carriage blocks, said holddown means comprising a plate which is hingedly mounted on said lower plate, whereby said holddown plate may be swung upward about the hinge axis away from the table surface to permit insertion thereunder of a workpiece to be stitched and may be swing downwardly toward the table surface upon the inserted workpiece to clamp said workpiece under said holddown plate.
 10. An apparatus for guiding work to be stitched along a predetermined path through the stitching zone of a sewing machine, said machine having a reciprocating needle in said stitching zone, which apparatus comprises a table having a surface which has a low coefficient of friction on which the work to be stitched is slidable; a horizontally disposed pattern plate; means mounting said pattern plate in stationary fixed position on said table; a cam track slot having a straight portion and a curved portion in said pattern plate shaped to the contour of the seam to be stitched in said work; a cam track follower movable along and guided by said cam track from a starting position in a forward stroke to a stopping position and in a retraction stroke back to said starting position; a first windup pulley above said table surface having a vertically disposed rotatable shaft fixed thereto and extending downwardly through said table; a speed reducer having a rotatable input and a rotatable output shaft; a prime mover comprising a sewing machine transmitter means mounted under said table having a drive shaft; a rotatable motion-transmitting shaft rotated by said drive shaft; an adjustable variable speed drive mechanism connected with the input shaft of said speed reducer and said rotatable motion-transmitting shaft; clutch means connecting the output shaft of said speed reducer and the downwardly extending shaft of said first windup pulley, said clutch means being adjustable to a first position in which the clutch is in slipping engagement and to a second position in which said clutch is fully engaged; a first cable connected at one end with said cam track follower to travel therewith and at its other end to the periphery of said first windup pulley, said first windup pulley being driven in a given angular direction when said clutch is in said second position and fully engaged, causing said cam follower to travel along said cam track in a forward stroke from said starting position to said stopping position; a second windup pulley above said table surface having a vertically disposed, rotatable shaft fixed thereto and extending downwardly through said table; a gearwheel secured to said second windup pulley shaft; a first compressed air cylinder mounted under said table the piston of which is secured to a gear rack meshing with said gearwheel and exerting a yieldable torque on said gearwheel; a second cable connected at one end to said cam trAck follower to travel therewith and at its other end to the periphery of said second windup pulley, said second windup pulley being rotated by said gearwheel to wind up said second cable when said clutch is in said first position and causing said cam track follower to travel along said cam track in a retraction stroke from said stopping position back to said starting position, when said clutch is in said first position in slipping engagement; a first carriage means movable in one coordinate direction and in response to movement of said cam track follower, said first carriage means including blocks slidably mounted on a pair of parallel first guide rails fixedly mounted on a pair of stationary blocks secured to said table; a second carriage means movable in a second coordinate direction perpendicular to said first-mentioned coordinate direction and operatively connected with said cam track follower and movable in said second coordinate direction in response to movement of said cam track follower, said second carriage means including blocks slidably mounted on a pair of parallel second guide rails mounted at right angles to said pair of first guide rails, said second guide rails being mounted on the blocks of said first carriage means; a carriage plate secured to the blocks of said second carriage means; a work holddown plate hingedly connected to said carriage plate and positioned adjacent the surface of said table and swingable about the axis of said hinge connection in a downward direction for clamping the workpiece thereunder and in upward direction for unclamping and releasing the workpiece clamped thereunder, said holddown plate causing the workpiece clamped thereunder to slide on said table surface through the stitching zone of the sewing machine, said holddown plate having a slot therein corresponding with the shape of said cam track slot through which said needle reciprocates; a compressed air cylinder having a piston with means engageable with said holddown plate for swinging said holddown plate in upward direction; rotatable guide means engaged by said cables, including pulleys mounted for rotation adjacent the curved portion of said cam track slot over which said cables are trained; the combined movement of said carriages in response to movement of said cam track follower causing the work holddown plate and the work clamped under said holddown plate to move on said table surface through said stitching zone in a path which has the same contour as the contour of said cam track, so that said needle sews a seam in the work having the same contour as the contour of said cam track of the pattern plate.
 11. Apparatus according to claim 10, wherein a compressed air cylinder is provided having a reciprocating piston rod including means which is engageable with said holddown plate and which urges said holddown plate downwardly when said rod is extended and which permits said holddown plate to be lifted upwardly when said piston rod is retracted.
 12. Apparatus according to claim 11, which includes electric power circuitry and a compressed air power system for automatic control of the operation of the apparatus, said apparatus including a light source, a light-sensitive cell in line with a beam of light from said light source and connected in said electric circuitry, said cell being operative to control the stopping of the stitching operation at a predetermined stage in the cycle of movement of said holddown plate.
 13. Apparatus according to claim 12, in which said rotatable guide means comprise at least two pulleys mounted for rotation about a common axis, the center of which lies at the center curvature of the curved portion of said cam track slot, one of said pulleys lying in the same plane as said first windup pulley and having said first cable trained thereover, and the second of said two pulleys lying in the same plane as said second windup pulley and having said second cable trained thereover, and a third idler pulley over which said second cable is trained and lying in the plane of said second windup pulley.
 14. Apparatus according to claim 13, wherein the guide pulley over which said first cable is trained has a segmental cutout portion at its periphery serving as a stop means to limit the amount of angular rotation of said first cable guide pulley in the direction of said first windup pulley.
 15. An apparatus for guiding work to be stitched along a predetermined path through the stitching zone of a sewing machine, said machine having a reciprocating needle in said stitching zone, which apparatus comprises a table having a work-supporting surface; a stationary pattern plate; a cam slot in said pattern plate shaped to the contour of the seam to be stitched in said work; a follower member movable along and guided by said cam slot; power means comprising power-operated first drive means for moving the follower member along said slot during the sewing operation from a starting position to an end position in synchronization with the operation of the sewing machine and power-operated second drive means for returning the follower to the starting position after termination of the sewing operation, the second drive means being operable independently of both the first drive means and the sewing machine; carriage means connected with and movable in response to movement of said cam follower member; a work holddown member connected with and movable in response to movement of said carriage means; said holddown member having a needle slot therein through which said needle is reciprocable and corresponding in shape to the contour of said cam slot, said holddown member being operable to retain the work against said work-supporting surface and to release the work; said holddown member moving in response to movements of said carriage means and follower member in a path coincident with the path of travel of said follower member; means operative to move said holddown member into and away from its work retaining position; said holddown member being operative, when said machine is operated, to move the work retained thereby through said stitching zone in a path corresponding to the contour of said cam slot to thereby cause the machine to stitch a seam in the work having the same contour as the contour of said cam slot.
 16. Apparatus according to claim 15 in which said holddown member includes an opening providing a window adjacent the needle slot in said holddown member; a shutter means in said opening operable to provide a gap near said needle through which work under said holddown member may be observed prior to the stitching operation and operable to place said shutter in a position for clamping said work under said holddown member.
 17. Apparatus according to claim 16 in which said shutter is pivotally mounted on said holddown member and in which power means are connected to said shutter for swinging said shutter about its pivot to an open position to provide said gap and to a closed position for clamping the work under said holddown member.
 18. Apparatus according to claim 17 in which said power means comprises an air cylinder mounted on said holddown member and having a piston rod operatively connected to said shutter. 